Introduction to Realtime Systems

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Introduction to Realtime Systems Embedded
Systems

• B. Ramamurthy
• CSE321
• This course is partially supported National
  Science Foundation NSF DUE Grant 0737243

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The course will enable you to

• Understand and design embedded systems and
  real-time systems
• For real-time systems
• Identify the unique characteristics of real-time
  systems
• Explain the general structure of a real-time
  system
• Define the unique design problems and challenges
  of real-time systems
• Apply real-time systems design techniques to
  various software programs.

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Course overview

• For embedded systems it will enable you to
• Understand the basics of an embedded system
• Program an embedded system
• Design, implement and test an embedded system.
• Ex realtime embedded games on a Gameboy or
  arcade games
• Ex realtime Spore on a laptop

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Global Embedded Systems Market

• Global Embedded Systems Market, 2003-2009(
  Millions)
• Source BBC Inc.

http//www.the-infoshop.com/study/bc31319-embedded
-systems.html
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Example real-time and embedded systems
Domain Application
Avionics Navigation displays
Multimedia Games simulators
Medicine Robot surgery remote surgery medical imaging
Industrial systems Robot assembly lines automated inspection
Civilian Elevator control Automotive system Global positioning system (GPS)
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Lets discuss some realtime system (RTS)
characteristics
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Realtime Characteristics

• RTS have to respond to events in a certain
  pre-detemined amount of time.
• The time constraints have to be considered during
  planning, design, implementation and testing
  phases.
• Internal failures due to software and hardware
  fault have be handled satisfactorily.
• You cannot simply pop-up a dialog error box that
  says send report or dont send report.
• Also external failures due to outside sources
  need to be handled.

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Realtime Characteristics (contd.)

• Typical interaction in an RTS is asynchronous.
  Thus an RTS should have features to handle
  asynchronous events such as interrupt handlers
  and dispatcher and associated resources.
• Potential for race condition when state of
  resources are timing dependent race condition may
  occur.
• Periodic tasks are common.

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Embedded System

• Is a special purpose system designed to perform a
  few dedicated functions.
• Small foot prints (in memory)
• Highly optimized code
• Cell phones, mp3 players are examples.
• The components in an mp3 player are highly
  optimized for storage operations. (For example,
  no need to have a floating point operation on an
  mp3 player!)

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Real-time system concepts

• A system is a mapping of a set of input into a
  set of outputs.
• A digital camera is an example of a realtime
  system set of input including sensors and
  imaging devices producing control signals and
  display information.
• Realtime system can be viewed as a sequence of
  job to be scheduled.
• Time between presentation of a set of inputs to a
  system and the realization of the required
  behavior, including availability of all
  associated outputs, is called the response time
  of the system.

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Real-time system concepts (contd.)

• Real-time system is the one in which logical
  correctness is based on both the correctness of
  the output as well as their timeliness.
• A soft real-time system is one in which
  performance is degraded by failure to meet
  response-time constraints.
• A hard real-time system is one in which failure
  to meet a single deadline may lead to complete
  and catastrophic failure.
• More examples
• Automatic teller soft
• Robot vacuum cleaner firm
• Missile delivery system hard

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Regular Computer System
Program
From Minimalist STIR-FRIED CHICKEN WITH
CREAMED CORN Time 20 minutes 1 pound boneless
chicken (breasts or thighs), in 1/2-inch chunks
2 tablespoons soy sauce 1 teaspoon sesame oil
1 tablespoon sherry, rice wine, sake or white
wine 2 tablespoons peanut oil or another neutral
oil, like corn or grape seed 1 tablespoon minced
garlic 1 tablespoon minced ginger 1 small
chili, seeds and stems removed, minced (or dried
red chili flakes to taste) 1 15-ounce can
creamed corn 1 cup corn kernels (fresh, frozen
or canned) Chopped cilantro leaves for garnish.
1. In a small bowl, mix the chicken with the
soy sauce, the sesame oil and the wine. Put the
peanut oil into a deep skillet or wok, preferably
nonstick, and turn heat to high. Drain chicken.
When oil is hot, add chicken to skillet, and
cook, undisturbed, until bottom browns, about 2
minutes. Stir once or twice, and cook 2 minutes
longer. Turn the heat down to medium-low. 2. Add
the garlic, the ginger and the chili to the
skillet, and stir 15 seconds later, add the
creamed corn and the corn kernels. Cook, stirring
occasionally, until heated through, 3 or 4
minutes. Garnish, and serve over white rice.
Data
Algorithm
Hardware
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Embedded Systems
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The Number Game (1)
1 3 5 7
9 11 13 15
17 19 21 23
25 27 29 31
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The Number Game (2)
2 3 6 7
10 11 14 15
18 19 22 23
26 27 30 31
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The Number Game (4)
4 5 6 7
12 13 14 15
20 21 22 23
28 29 30 31
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The Number Game (8)
8 9 10 11
12 13 14 15
24 25 26 27
28 29 30 31
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The Number Game (16)
16 17 18 19
20 21 22 23
24 25 26 27
28 29 30 31
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Analysis

• What is theory /concept behind this game?
• How did I arrive at the number you guessed?
• How can I automate this process?
• What is the data and what is the algorithm?
• How can we convey these to a computing machine?
• While a computer talks binary, we humans write
  programs in languages such as Java, C, C,
  Basic etc.
• Binary numbers (1s and 0s) is the number system
  used by the computer systems.
• We humans use decimal number system that has 10
  distinct symbols (0,1,2,3,4,5,6,7,8,9)
• Your task Write a C program to computerize this
  game.

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2 3 6 7
10 11 14 15
18 19 22 23
26 27 30 31
1 3 5 7
9 11 13 15
17 19 21 23
25 27 29 31
16 17 18 19
20 21 22 23
24 25 26 27
28 29 30 31
4 5 6 7
12 13 14 15
20 21 22 23
28 29 30 31
8 9 10 11
12 13 14 15
24 25 26 27
28 29 30 31
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Summary

• We examined the course objectives for embedded
  and realtime systems
• We looked at sample systems
• Homework
• Write a program that automates the number game